Every day, an estimated 1,000 newcomers are born into or move to Bombay, a city of 12.6 million and a metropolitan area of 15 million, that already ranks among the world's most crowded places.
Within 20 years, the greater metro area is projected to reach 27.4 million people, nearly the current population of Canada.Congested, chaotic, frenetic and frayed, the world's cities have never been so popular. Soon, for the first time in history, more humans will live in urban areas than in rural ones, as developing countries undergo an almost unparalleled transformation.
Through birth more than migration, the world is adding 200,000 new city dwellers every week and is likely to continue to do so for the next 30 years. In one generation, cities like Jakarta, Tehran and Sao Paulo have tripled in size to reach populations that are greater than those of most members of the United Nations.
If there were any doubt, we have become an urban species, living not in a global village but a global city. In the next century, there will be as many as 1,657 cities with populations in excess of one million people. In the last century, there was only one: London.
And the majority of the big new cities will be in Asia. Fewer than one in five will be in Europe and North America.
"Urbanization is desirable. It is inevitable. It is an unstoppable phenomenon," said O.P. Mathur, an urban specialist at India's National Institute of Public Finance and Policy.
But how much urbanization can the world take? The United Nations is trying to find out at its second-ever Conference on Human Settlements, known as "Habitat 2," in Istanbul, Turkey, a city of 7.8 million that has seen urban societies rise and fall for millennia.
When the first U.N. Habitat conference was held in 1976, the world believed in fix-it urban development, a belief that investments in sewers, water pipes, roads and mass transit systems would cure the ills of a city.
Twenty years later, with cities bursting at the seams, there is less faith in such solutions and more concern with management; less focus on fixing cities and more focus on fixing city halls. The reason is that the explosion of cities is seen mostly in developing countries, the places that can least afford the urban infrastructure to serve such large numbers.
In the year 2015, the world's 10 largest cities will not include New York, Los Angeles or London. The great metropolises of the 20th century will be replaced by the likes of Lagos, Shanghai, Jakarta and Dhaka, each with populations greater than that of present-day Australia.
Even more daunting challenges may lie away from the national capitals and megacities, in the hundreds of towns and trading centers that will become major cities, in size if not stature - places like Surat, India, already home to 1.5 million but with no garbage collection, no waste-water treatment and an outbreak of bubonic plague in 1994.
For all their faults, however, cities have become humanity's residence of choice.
"If you only see cities as statistical numbers, it can be quite frightening," said Bombay's best-known architect and planner, Charles Correa. "What those figures don't take into account is that these are human places."
But the appeal of a city is much more than the sum of development statistics and consumer products. The agglomeration of humans - creative, consuming humans - has fostered the world's dominant social and political cultures. Cities allow for universities, theaters, community groups, sports leagues and ideas, from the French Revolution in Paris to Burma's modern-day struggle for democracy in Rangoon.
Often seen as fat cats, cities have been ignored, even abused, by national and state governments. They often get the smallest slice of a tax pie even though they have the biggest plate to fill. Many can't raise their own investment capital to finance transit systems and sewers, or even set their own laws and regulations, without higher approval.
That may change as cities become the dominant voting centers in most countries. But strong city councils aren't enough to make a city work. Long-term investments in public transport, thoughtful regional planning, active communities, vibrant and diverse economies, free and fair housing markets - these are some ingredients of success that soon will be needed in abundance, and not just for those who live in cities.
As the world prepares for its first urban millennium, the humans who once defined the city are now defined by it, too.
(Distributed by Scripps Howard News Service.)